Decks & Pergolas instruction manual

All,

I am past the point now where nothing seems to make sense to me. I have bought the book above recommended by a number of people on how to build my deck. I am struggling in trying to work out how to use the span tables.

Can anybody help. This is what I think so far:

Bearers - Continuous span:

The load width is the distance either side of the post in which the bearer is supporting (equal distance). The table gives sizes vertically ranging from 1800-3600. The table headings going across the top states "size of bearers (mm) for bearer span (m) and also gives similar values except it starts at 1200-3000. What is this for?

Can somebody please give me some sort of idiots instruction in how to read this. Never did I think that I would come across a table that creates so much confusion.

Continuos span is where the bearer (or joist) is on at least 3 supports.
Single span = 2 supports (one each end)

Load width how much the bearer supports either side. Imagine you are holding one end of a piece of timber in your right hand, and a mate at the other end. You both hold 1/2 the weight. In your lteft hand you holdanother piece and another mate has the other end, again you hold 1/2 a piece. All up you hold the equivalent of one full piece.


likewise load width is 1/2 the span to both sides of the bearer.
eg bearers 1000 apart. Load width = 500 (one side) + 500 (other side) = 1000. The bearer at the edge would only have a load width of 500, as there is nothing on the other side.

If they are equally spaced, Load width is equal to the bearer spacing. otherwise it is 1/2 + 1/2


SPAN TABLES
The figures across the top are the bearer span i.e. distance between stumps. The vertical figures are the load widths.


So for example I want stumps 1600 apart, and bearers 2000 spacing. Read across the top to 1600. If 1600 not there go to the next highest figure. then go down the side to the load width to 2000, (or the next highest figure.)

Where those 2 columns meet is the size of bearer you need.

If you bought the Allan Staines book there is a diagram of how to read each chart above the chart....


Joist span is measured from bearer to bearer...

A continuous span is a joist or bearer thats supported over atleast 3 points of similar distance apart

If its supported only at each end then its a single span

Bearer span is measured from support to support.. Its load width is half of the joist span on either side of it if its in the middle or half of one side if its at the front


Cheers utemad